1. Field of the Invention
The present invention relates in general to interfacing of a personal computer, referred to hereinafter as PC, to the peripheral equipments, and more particularly to a method and a system for interfacing a PC to CD-ROM drives wherein the interfacing time of the PC can efficiently be managed suitably to a high speed operation of the system when the PC is connected to a plurality of CD-ROM drives.
2. Description of the Prior Art
Methods of interfacing a PC to CD-ROM drives may generally be classified into two types. The first method is a standard method for interfacing of a small computer system, which is broadly used in that it has the advantage of providing compatibility and a variety of functions for the computer system. The second method is that provides an interfacing method and a circuit thereof suitable to the internal structure and functions of a host computer. The second method has the advantage, in that the optimum computer architecture is enabled in consideration of the functions and performance of the PC used as the host computer and the cost thereof is low.
The interfacing of the PC to the CD-ROM drives based on the second method is illustrated in FIG. 1. As shown in this drawing, in the case where the PC as the host computer is connected to the CD-ROM drives via an interface bus, first at a bus free state (S1), the host PC selects one of the CD-ROM drives required to communicate therewith, as a target, at a step S2. Then at a step S3, the host PC generates a control command for instructing the DC-ROM drive selected as the target to transmit information data and target status data thereto. In response to the control command, the CD-ROM drive selected as the target prepares for the information data and the status data to be transmitted to the host PC. Upon completion of the preparation for the information data and the status data, the target CD-ROM drive transmits the information data and the status data to the host PC at steps S4 and S5. When the data transmission from the target to the host PC is completed, the bus through which the host PC is connected to the target is made the free state (S1) and the host PC proceeds to a different job.
However, the first method has a disadvantage, in that it has no regard for the internal functions and performance of the PC used as the host computer. Although the PC has been designed to utilize functions of various peripheral equipments, the interfacing is performed only based on the standard method, such that the PC does not utilize fully transmission speeds, respectively, suitable to the peripheral equipments and other functions. Since the PC does not utilize fully a multiplicity of functions thereof, it may become "over spec". Moreover, the cost of the interfacing hardware and software is high.
Also, the second method has a disadvantage, in that the interfacing hardware and software are provided suitably to a variety of types of the PC, resulting in provision of no compatibility with one another. Moreover, after the host PC selects the target CD-ROM drive and generates the command thereto, it waits for the target CD-ROM drive to transmit the information data and the status data thereto, without performing other jobs. Because the CD-ROM drive has the access time longer than those of other recording media such as a hard disk drive (HDD) (i.e., 500-900 msec. in the CD-ROM drive while several tens msec. in the HDD), it has the long preparation time for the data to be transmitted to the host PC. For this reason, the interfacing time becomes long. Furthermore, when the interfacing is carried out between the host PC and any one of the peripheral equipments, the communication of the host PC with the other peripheral equipments is made impossible. This results in an inefficiency of the interfacing.